Good question.
The two main variants, ie FAW.1, 4, & 5, with British AI.17 radar and the FAW.2, 6, & 8 with American AI.22 radar are all quoted as 56ft 4ins (or 56ft 3in) in every publication that I’ve got.
My understanding is that the airframe of the American equiped variants is shorter in the nose, but the radome is longer than that of the British equiped ones, thus possibly making up the similar overall length. Worth noting that the radome to fuselage joint is asymetric (diagonal when seen in plan view) on these types.

Having said that, when you look at pictures of the two variations there does seem to be a good foot or so difference in the overall length ahead of the windscreen area!

Be interesting to see all the variants lengths form AP/PNs sources, which I would think is the only sure fire way of finding out.